Re: [PATCH] fat: Support fallocate on fat.

[Namjae Jeon]

2012/7/9, OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>:
> Namjae Jeon <linkinjeon@xxxxxxxxx> writes:
>
>>>> +	/*
>>>> +	 * calculate i_blocks and mmu_private from the actual number of
>>>> +	 * allocated clusters instead of doing it from file size.This ensures
>>>> +	 * that the preallocated disk space using FALLOC_FL_KEEP_SIZE is
>>>> +	 * persistent across remounts and writes go into the allocated
>>>> clusters.
>>>> +	 */
>>>> +	fat_calc_dir_size(inode);
>>>
>>> Looks like the wrong. If you didn't initialize preallocated space, the
>>> data never be exposed to userland. It is security bug.
>> As explained above, if we do append write instead of seeking into a
>> random offset, there is no security risk.
>
> So it means? - if we didn't, there is.
Yes, right.
>
>> The main disadvantage with initializing the preallocated space (as is
>> done in case of without FALLOC_FL_KEEP_SIZE ) is it takes long time
>> for bigger allocation sizes. It took ~70 seconds to preallocate 2GB on
>> our target if FALLOC_FL_KEEP_SIZE is not set.
>
> It doesn't become the reason to expose uninitialized data.
I agree.. If I try to change code for initializing the preallocated
space, Is this patch acceptable ?

Thanks Ogawa.
>
> Thanks.
> --
> OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/